QUANTIFICATION OF HUMAN AMNIOTIC-FLUID CONSTITUENTS BY HIGH-RESOLUTION PROTON NUCLEAR-MAGNETIC-RESONANCE (NMR) SPECTROSCOPY

We have investigated the ability of high-resolution proton NMR spectro scopy to provide a biochemical constituent screening of human amniotic fluid (AF). Proton NMR spectra were obtained at 300 MHz on AF from pa tients undergoing amniocentesis in the mid-trimester. Only AF from nor mal pregnancies (normal fetal karyotype, normal alpha-fetoprotein leve ls, normal birth outcome) was used in this study. The AF supernatant w as lyophilized and resuspended in deuterated water containing 0-1 mm p hosphate buffer and 6.02 mm disodium maleate. Identification of low mo lecular weight compounds was confirmed by two-dimensional NMR spectra (primarily correlated spectroscopy, or COSY) and standard addition tec hniques. A broad profile of compounds were 'NMR visible' in a single p roton spectrum, including creatinine, glucose, organic acids (acetate, citrate, and lactate) and several amino acids (alanine, histidine, le ucine, phenylalanine, tyrosine and valine). The proton spectrum was un affected by prior freezing/thawing of AF samples. We were able to quan tify compounds by comparison with an added concentration standard (mal eate) at concentrations as low as 30 mum. Good agreement with literatu re values based on other analytical techniques was obtained.